A recent theoretical literature highlights the role of endogenous firm entry as an internal amplification mechanism of business cycle fluctuations. The amplification mechanism works through the competition effect (CE) and the variety effect (VE). This paper tests the significance of this amplification mechanism, quantifies its importance, and disentangles the CE and VE. To this end, we estimate a medium-scale real business cycle model with firm entry for the U.S. economy. The CE and VE are estimated to be statistically significant. Together, they amplify the volatility of output by 8.5% relative to a model in which both effects are switched off. The CE accounts for most amplification, whereas the VE only plays a minor role.
